1. Field of the Invention
The present invention relates to an attachment film for use in electronic displays such as Cathode Ray Tube (CRT) and a liquid crystal display device. More specifically, it relates to a an attachment film for an electronic display, which is for adjusting the quantity of transmitted light from a light source and the scattering of transmitted light and for preventing the reflection of a fluorescent lamp and sun light in and from a display device screen.
2. Description of the Prior Art
Conventionally, a glass unit as a screen of a display device such as a plasma display or TV cathode ray tube contains a colorant such as carbon black. The colorant is used for adjusting the quantity of transmitted light from a light source. For example, in a cathode ray tube having a fluorescent material which forms a color by the irradiation with electron beams, white is formed by mixing three colors such as red, green and blue, and black is formed in a color-non-forming portion. As a result, the cathode ray tube has a characteristic that the intensity of white is high and the intensity of black is low. A glass unit as a display device screen is therefore colored in gray for controlling white and intensifying black. In recent years, there are increasingly used displays having a cathode ray tube, etc., of which the light source side is formed as a curved surface and the viewer side, i.e., the front side is formed as a flat surface. In a display of the above type, the screen of a glass unit has a small thickness in the central portion thereof, and the thickness increases toward circumferential portions. In the above glass unit having a change in thickness, the central portion is required to be colored densely, and it is required to decrease the coloring toward the circumferential portions, for accomplishing a uniform optical transmissivity and a uniform scattering ratio of the glass unit on the entire screen of the glass unit. However, the decreasing the coloring toward the circumferential portions of the glass unit makes its production process complicated and requires an additional cost. Further, it is required to alter a gray scale variously depending upon a colorant used or a display material used. The coloring of the glass unit for satisfying the above demands is liable to make the production process thereof complicated and incur an increase in its production cost. Further, with an increase in the size of a display, a fluorescent lamp and sun light is reflected in the screen to a greater extent, and it is more intensely demanded to prevent the above reflection. When the optical transmissivity and the scattering ratio of the glass unit as a display device screen does not match a display material, a black and white contrast is deteriorated, and images showing original hues can be no longer viewed. It has been also found according to further studies that an adhesive layer of a film attached to the surface of an electronic display suffers air bubbles in some cases. More specifically, it has been found that air bubbles are formed in an adhesive layer in a light resistance test using the irradiation with ultraviolet light. The formation of air bubbles downgrades displayed images.
It is an object of the present invention to provide an attachment film for an electronic display, which film is used for adjusting the optical transmissivity depending upon a variety of electronic displays and adjusting color shades.
It is another object of the present invention to provide an attachment film for an electronic display, which film permits the simple and easy adjustment of the reflection of a fluorescent lamp and sun light in and from the screen thereof.
It is further another object of the present invention to provide an attachment film for an electronic display, which film can serve to adjust the optical transmissivity, adjust color tones and prevent the reflection of a fluorescent lamp and sun light in a screen even when the electronic display is increased in size.
It is still further another object of the present invention to provide an attachment film for an electronic display, which film can prevent the formation of air bubbles in an adhesive layer thereof.
According to the present invention, there is provided an attachment film for an electronic display, which comprises an adhesive layer which contains carbon black dispersed therein and is formed on one surface of a transparent substrate.
According to the present invention, there is provided an attachment film according to the above, wherein the adhesive layer further contains a coloring pigment different from the carbon black.
According to the present invention, there is provided an attachment film according to the above, wherein the attachment film is colored in neutral gray.
According to the present invention, there is provided an attachment film according to the above, wherein the carbon black in the adhesive layer has an average particle diameter of 30 nm or less and has a BET specific surface area of at least 100 m2/g.
According to the present invention, there is provided an attachment film according to the above, wherein the adhesive layer contains an acrylic adhesive having a carboxyl group and/or a hydroxyl group and the carbon black is an acidic carbon black.
According to the present invention, there is provided an attachment film according to the above, wherein the adhesive layer further contains a photopolymerizable compound and a photopolymerization initiator.
According to the present invention, there is provided an attachment film according to the above, wherein the adhesive layer is formed on one surface of the transparent substrate and a hard coating layer and an anti-reflection layer are consecutively formed on the other surface of the transparent substrate.